diff --git a/Makefile.in b/Makefile.in
index 565c370ea6d..b657ad6a688 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -81,10 +81,9 @@ endif
 
 ifdef CFG_ENABLE_DEBUG
   $(info cfg: enabling more debugging (CFG_ENABLE_DEBUG))
-  CFG_RUSTC_FLAGS += -g --cfg=debug
+  CFG_RUSTC_FLAGS += -g
   CFG_GCCISH_CFLAGS += -DRUST_DEBUG
 else
-  CFG_RUSTC_FLAGS += --cfg=ndebug
   CFG_GCCISH_CFLAGS += -DRUST_NDEBUG
 endif